1. Field of the Invention
The present invention relates to a method for mounting semiconductor elements, and more particularly, to a method for mounting semiconductor elements by connecting semiconductor elements with a wiring substrate using flip-chip mounting.
2. Description of Related Art
A flip-chip bonding method, known as one of semiconductor element assembling techniques, is a method for connecting a solder bump on an electrode provided on the bottom surface of a semiconductor element with a facing solder bump on a connecting pad provided on the upper surface of a wiring substrate. Since flux was used in the conventional flip-chip bonding method, the oxide film on the surface of the solder bump was removed facilitating connection using solder. However, this method had a problem in that the flux remained as a residue after the cleaning step unless the quantity of the flux was optimized, or the cleaning step was properly controlled, and the residue of the flux interfered with the injection of the sealing resin in the following step. Furthermore, this method had another quality assurance problem in that the residue of the flux induced the occurrence of migration lowering the reliability of connection.
As described above, since flux is used in the conventional flip-chip bonding method, the method had a problem of the lowered reliability of connection due to the residue of flux remaining after the cleaning step.